Gerund Pipe Industry

Product Description
Seam pipe refers to a steel pipe in which the weld seam is parallel to the longitudinal direction of the steel pipe. It is also generally called straight seam welded pipe or straight seam steel pipe. Straight seam pipes are made by rolling long strips of steel strips of a certain specification through high-frequency welding units and using straight seam welding. The specifications of straight-seam pipes are expressed in nominal diameter. According to the wall thickness, they can be divided into two types: thin-walled straight-seam pipes and thick-walled straight-seam pipes. According to the shape, it can be divided into round, square or special-shaped tubes.
Process of seam pipes
Seam pipes generally use high-frequency welding. High-frequency welding is a kind of induction welding (or pressure contact welding). It does not require weld filler, welding spatter, and welding heat-affected zone. It has the advantages of narrow, beautiful welding shape and good welding mechanical properties, so it is widely used in the production of steel pipes. According to the principle of electromagnetic induction and the skin effect, proximity effect and eddy current thermal effect of AC charges in the conductor, the steel at the edge of the weld is locally heated to a molten state. After being squeezed by the roller, the butt weld is inter-crystal bonded, thereby achieving The purpose of welding is to form a strong straight seam after cooling.
Execution standards and materials of seamed pipes
Seamed pipes generally adopt / and / standards. Commonly used materials include,,,,,.
Uses of seamed pipes
Seamed pipes are mainly used in water supply projects, petrochemical industry, chemical industry, electric power industry, agricultural irrigation, and urban construction in China. Used for water supply and drainage for liquid transportation. For gas transportation, coal gas, steam, and liquefied petroleum gas are used. It is used as piling pipes for structures, pipes for bridges, wharves, roads, building structures, etc.


Straight seam pipe is a type of steel pipe, which refers to a steel pipe in which the weld seam is parallel to the longitudinal direction of the steel pipe. According to the wall thickness, there are thin-walled straight seam pipes and thick-walled straight seam pipes. According to the shape, there are round pipes, square pipes or special-shaped pipes. According to the uses, there are general welded pipes, galvanized welded pipes, oxygen blown welded pipes, wire casings, and metric welded pipes. , idler pipes, deep well pump pipes, automotive pipes, transformer pipes, electric welded thin-walled pipes, electric welded special-shaped pipes and spiral welded pipes. Straight seam pipe refers to a steel pipe whose weld seam is parallel to the longitudinal direction of the steel pipe. It is also generally called straight seam welded pipe or straight seam steel pipe. Straight seam pipes are made by rolling long strips of steel strips of a certain specification through high-frequency welding units and using straight seam welding. The specifications of straight-seam pipes are expressed in nominal diameter. According to the wall thickness, they can be divided into two types: thin-walled straight-seam pipes and thick-walled straight-seam pipes. According to the shape, it can be divided into round, square or special-shaped tubes.
Classified by weld shape
Can be divided into straight seam welded pipes and spiral welded pipes
Straight seam welded pipes have simple production process, high production efficiency, low cost and rapid development.
The strength of spiral welded pipes is generally higher than that of straight seam welded pipes. Welded pipes with larger diameters can be produced from narrower billets, and welded pipes with different diameters can also be produced from billets of the same width. However, compared with straight seam pipes of the same length, the weld length is increased by ~%, and the production speed is lower. Therefore, smaller diameter welded pipes mostly use straight seam welding, while large diameter welded pipes mostly use spiral welding.


Classification by use
Classification by use: general welded pipe, galvanized welded pipe, oxygen blown welded pipe, wire casing, metric welded pipe, roller pipe, deep well pump pipe, automobile Used pipes, transformer pipes, electric welded thin-walled pipes, electric welded special-shaped pipes and spiral welded pipes.
General welded pipes General welded pipes are used to transport low-pressure fluids. Made of steel. It can also be made of other mild steels that are easily weldable. Steel pipes need to undergo experiments such as hydraulic pressure, bending, and flattening, and have certain requirements for surface quality. The delivery length is usually 10,000 square meters, and it is often required to be delivered in a fixed length (or multiple lengths). The specifications of welded pipes are expressed in nominal diameter (millimeters or inches). The nominal diameter is different from the actual. According to the specified wall thickness, there are two kinds of welded pipes: ordinary steel pipes and thickened steel pipes.
Galvanized steel pipe In order to improve the corrosion resistance of steel pipes, general steel pipes (black pipes) are galvanized. Galvanized steel pipes are divided into two types: hot-dip galvanizing and electric steel zinc. Hot-dip galvanizing has a thick zinc layer and electro-galvanizing has low cost.
Oxygen-blown welded pipes are used for oxygen-blown pipes in steelmaking. They are generally small-diameter welded steel pipes with eight specifications: inch by inch. Made of, or steel strips. To prevent corrosion, some are aluminized.
Wire sleeves are also ordinary carbon steel electric welded steel pipes, used in concrete and various structural power distribution projects. The commonly used nominal diameters range from . The wire sleeve has a thin wall and is mostly used after being coated or galvanized, requiring a cold bending test.
Metric welded pipe specifications are in the form of seamless pipes, welded steel pipes expressed in outer diameter * wall thickness in millimeters, welded with tropical or cold zone of ordinary carbon steel, high-quality carbon steel or general low alloy steel, or with After hot strip welding, it is made by cold drawing method. Metric welded pipes are divided into general-purpose and thin-walled pipes. They are generally used as structural parts, such as transmission shafts, or to transport fluids. Thin-walled pipes are used to produce furniture, lamps, etc. The strength and bending test of the steel pipe must be ensured.
The roller tube is used for belt conveyor roller electric welded steel pipe, generally made of steel and steel, diameter. There are certain requirements for the curvature of the pipe, the end face to be perpendicular to the center line, and the ovality. Generally, water pressure and flattening tests are performed.
Transformer tubes are used to manufacture transformer heat pipes and other heat exchangers. They are made of ordinary carbon steel and require flattening, flaring, bending and hydraulic tests. Steel pipes are delivered in fixed lengths or multiple lengths, and there are certain requirements for the bending of the steel pipes.
Special-shaped pipes are square pipes, rectangular pipes, hat-shaped pipes, hollow rubber steel pipes for doors and windows welded from ordinary carbon structural steel and equal steel strips. They are mainly used as agricultural machinery components, steel windows and doors, etc.
Welded thin-walled tubes are mainly used to make furniture, toys, lamps, etc. In recent years, thin-walled tubes made of stainless steel strips have been widely used in high-end furniture, decorations, fences, etc.
Spiral welded pipes are made by rolling low-carbon carbon structural steel or low-alloy structural steel strips into pipe blanks at a certain spiral angle (called forming angle), and then welding the pipe seams. It can be used Narrower strips produce larger diameter steel pipes. Spiral welded pipes are mainly used for oil and natural gas transmission pipelines, and their specifications are expressed by outer diameter * wall thickness. Spiral welded pipes are either single-sided or double-sided. Welded pipes should ensure that the hydraulic pressure test, tensile strength and cold bending performance of the weld meet the regulations.


Classified by end shape
It is further divided into round welded pipes and special-shaped (square, flat, etc.) welded pipes.
Classified by welded pipe material and use
/ (galvanized welded steel pipe for low-pressure fluid transportation). It is mainly used to transport water, gas, air, oil, heating hot water or steam and other general lower pressure fluids and other pipes. It stands for material grade steel.
/ (Galvanized welded steel pipe for low-pressure fluid transportation). Mainly used to transport water, gas, air, oil, heating hot water or steam and other general lower pressure fluids and other pipes. Its representative material is grade steel.
/ (Welded steel pipe for mining fluid transportation). It is mainly used for straight seam welded steel pipes for mine air pressure, drainage and shaft gas discharge. It represents material and grade steel. / (Large-diameter electric welded steel pipe for low-pressure fluid transportation). Mainly used for transporting low-pressure fluids such as water, sewage, gas, air, heating steam and other purposes. It stands for material grade steel.
/ (Stainless steel welded steel pipe for mechanical structure). Mainly used in machinery, automobiles, bicycles, furniture, hotel and restaurant decoration and other mechanical parts and structural parts. It represents material etc.
/ (Stainless steel welded steel pipe for fluid transportation). Mainly used to transport low-pressure corrosive media. The representative materials are,,,,,, etc.


Welding
Straight seam pipes generally use high-frequency welding. High-frequency welding is a kind of induction welding (or pressure contact welding). It does not require weld filler and no welding. It has the advantages of spatter, narrow welding heat-affected zone, beautiful welding shape, and good welding mechanical properties, so it is widely used in the production of steel pipes. According to the principle of electromagnetic induction and the skin effect, proximity effect and eddy current thermal effect of AC charges in the conductor, the steel at the edge of the weld is locally heated to a molten state. After being squeezed by the roller, the butt weld realizes inter-crystal bonding, thereby achieving The purpose of welding is to form a strong straight seam after cooling.
Weld seam gap
The strip steel is fed into the welded pipe unit. After being rolled by multiple rollers, the strip steel is gradually rolled up to form a round pipe blank with an opening gap. Adjust the reduction amount of the extrusion roller. , so that the weld gap is controlled at ~ and both ends of the weld are flush. If the gap is too large, the proximity effect will be reduced, the eddy current heat will be insufficient, and the inter-crystal bonding of the weld will be poor, resulting in lack of fusion or cracking. If the gap is too small, the proximity effect will increase and the welding heat will be too high, causing the weld to burn or form a deep pit after extrusion and rolling, affecting the surface quality of the weld.
Welding temperature
Made of low carbon steel, the welding temperature is controlled at ~°C, which can meet the pipe wall thickness ~ welding penetration requirements. The welding temperature is mainly controlled by adjusting the high-frequency eddy current thermal power and welding speed. When the input heat is insufficient, the heated weld edge cannot reach the welding temperature, and the metal structure remains solid, resulting in incomplete fusion or incomplete welding. When the input heat is too large, the heated weld edge exceeds the welding temperature, resulting in excessive Burn or droplets will form a molten hole in the weld.
Standard
Straight seam pipes generally adopt / and / standards.


Material
Commonly used materials for straight seam pipes include,,,,,.
Quality Inspection
According to the standards of "Welded Steel Pipes for Low-Pressure Fluid Transport", the surface quality of steel pipes should be smooth, and defects such as folding, cracks, delamination, and lap welding are not allowed. The surface of the steel pipe is allowed to have minor defects such as scratches, scratches, weld dislocations, burns and scars that do not exceed the negative deviation of the wall thickness. Thickening of the wall thickness at the weld and the presence of internal weld bars are allowed.
Straight seam pipes should be subjected to mechanical performance tests, flattening tests and flaring tests, and must meet the requirements stipulated in the standard. The steel pipe should be able to withstand a certain internal pressure. If necessary, a pressure test should be carried out to ensure that there is no leakage for one minute. It is allowed to use eddy current flaw detection method instead of hydrostatic test.
Eddy current flaw detection is carried out according to the standard of "Eddy Current Flaw Detection Inspection Method for Steel Pipes". The eddy current flaw detection method is to fix the probe on the frame, keep a distance between the flaw detection and the weld, and rely on the rapid movement of the steel pipe to conduct a comprehensive scan of the weld. The flaw detection signal is automatically processed and automatically sorted by the eddy current flaw detector to achieve flaw detection. the goal of. After flaw detection, the welded pipe is cut to the specified length with a flying saw, and is rolled off the production line via a flip frame. Both ends of the steel pipe should be flat-chamfered and marked, and the finished pipes should be packed in hexagonal bundles before leaving the factory.
Straight seam pipes are mainly used in water supply projects, petrochemical industry, chemical industry, electric power industry, agricultural irrigation, and urban construction. Used for water supply and drainage for liquid transportation. For gas transportation, coal gas, steam, and liquefied petroleum gas are used. It is used as piling pipes for structures, pipes for bridges, wharves, roads, building structures, etc.


Straight seam welded pipes are produced with steel strips. Pipes that are straight seam welded by high-frequency welding equipment are called straight seam welded pipes. (It is named because the welding joint of the steel pipe forms a straight line). Among them, there are different production processes according to different uses (which can be roughly divided into scaffolding pipes, fluid pipes, wire casings, bracket pipes, guardrail pipes, etc.)
Welded steel pipes are also called welded pipes. They are made of steel The strips are cut into narrow steel strips and then cold-wrapped into tubes using molds. A special welder then welds a pipe seam. The outer welds are polished and bright. The internal burrs of ordinary welded pipes cannot be punched. Only precision welded pipes are internally burred
Anti-corrosion welded steel pipes refer to steel pipes with seams on the surface that are made by bending and deforming steel strips or steel plates into circular, square and other shapes and then welding them. According to different welding methods, it can be divided into arc welded pipe, high frequency or low frequency resistance welded pipe, gas welded pipe, furnace welded pipe, Bondi pipe, etc. According to the shape of the weld, it can be divided into straight seam welded pipe and spiral welded pipe. Electrically welded steel pipes are used in oil drilling, machinery, and manufacturing industries. Furnace welded pipes can be used as water and gas pipes, etc. Large-diameter straight seam welded pipes are used for high-pressure oil and gas transportation, etc. Spiral welded pipes are used for oil and gas transportation, pipe piles, bridge piers, etc. Welded steel pipes have lower costs and higher production efficiency than seamless steel pipes.
The technical requirements and quality inspection of straight seam welded pipes are based on the standards of "Welded Steel Pipes for Low-Pressure Fluid Transport". The nominal diameter of the welded pipe is ~, and the nominal wall thickness is. ~ The length of the welded pipe is usually ~ meters, and can be determined according to The length of ruler or double ruler leaves the factory. The surface quality of steel pipes should be smooth, and defects such as folding, cracks, delamination, and lap welding are not allowed. The surface of the steel pipe is allowed to have minor defects such as scratches, scratches, weld dislocations, burns and scars that do not exceed the negative deviation of the wall thickness. Thickening of the wall thickness at the weld and the presence of internal weld bars are allowed. Welded steel pipes should undergo mechanical performance tests, flattening tests and expansion tests, and must meet the requirements stipulated in the standard. The steel pipe should be able to withstand a certain internal pressure. If necessary, a pressure test should be carried out to ensure that there is no leakage for one minute. It is allowed to use eddy current flaw detection method instead of hydrostatic test. Eddy current flaw detection is performed in accordance with the "Eddy Current Flaw Detection Inspection Method for Steel Pipes" standard. The eddy current flaw detection method is to fix the probe on the frame, keep a distance between the flaw detection and the weld, and rely on the rapid movement of the steel pipe to conduct a comprehensive scan of the weld. The flaw detection signal is automatically processed and automatically sorted by the eddy current flaw detector to achieve flaw detection. the goal of. After flaw detection, the welded pipe is cut to the specified length with a flying saw, and is rolled off the production line via a flip frame. Both ends of the steel pipe should be flat-chamfered and marked, and the finished pipes should be packed in hexagonal bundles before leaving the factory.
The materials commonly used in China for straight seam welded pipes are generally:,,,,,, etc.
Applications of straight seam welded pipes Straight seam welded pipes are mainly used in water supply projects, petrochemical industry, chemical industry, electric power industry, agricultural irrigation, and urban construction in China. Used for water supply and drainage for liquid transportation. For gas transportation, coal gas, steam, and liquefied petroleum gas are used. It is used as piling pipes for structures, pipes for bridges, wharves, roads, building structures, etc.


The welding process used in submerged arc welded straight seam steel pipes is submerged arc welding technology, using filler welding and particle protected flux submerged arc. The caliber of production can reach, which is the English abbreviation of submerged arc welded straight seam steel pipe. The production process of submerged arc welded straight seam steel pipe includes forming technology and roll forming submerged arc welding technology.

When the diameter is large, two steel plates may be used for rolling, which will form a double weld. It can implement the standard/low-pressure fluid steel pipe production standards, oil and gas steel pipe production and use standards, and can also implement the American steel pipe implementation standards. Production material. The main pressure-bearing parameters are / , which is the yield strength and which is the wall thickness. Now submerged arc welding has developed into double-wire submerged arc welding and multi-wire submerged arc welding, and the efficiency has been further improved. It is widely used in steel structures, piling, fluid transportation, long-distance pipelines, etc.

Commonly used domestic materials for submerged arc welded straight seam steel pipes are,,,,,, etc.


High-frequency straight seam steel pipes. All straight seam steel pipes, thermal expansion pipes, etc. are produced using strip steel as the raw material, and the pipes obtained by straight seam welding on high-frequency welding equipment are called straight seam steel pipes. Sewing steel pipe. (It is named because the welding joint of the steel pipe forms a straight line).

High-frequency straight seam steel pipes have different uses and different subsequent production processes (can be roughly divided into scaffolding pipes, fluid pipes, wire casings, bracket pipes, guardrail pipes, etc.). High-frequency and induction heating technologies currently have the highest heating efficiency and fastest speed for metal materials, and are low-consumption and environmentally friendly. It has been widely used in thermal processing, heat treatment, thermal assembly, welding, smelting and other processes of metal materials in various industries. It can not only heat the entire workpiece, but also perform targeted heating of local parts of the workpiece to achieve deep heat penetration of the workpiece. It can also only focus on heating the surface and surface layer. It can not only directly heat metal materials, but also can heat non-metallic materials. Indirect heating. etc. Therefore, induction heating technology will be used more and more widely in various industries.

Commonly used domestic materials for high-frequency straight seam steel pipes are,,,,,, etc.


Thick-walled straight-seam steel pipes, steel pipes whose outer diameter and wall thickness ratio are less than that are called thick-walled straight-seam steel pipes. It is mainly used as petroleum geological drilling pipes, cracking pipes for petrochemical industry, boiler pipes, bearing pipes, and high-precision structural pipes for automobiles, tractors, and aviation.

The biggest difference between thick-walled straight-seam steel pipes and thin-walled straight-seam steel pipes is the thickness of the steel pipe wall. It is generally believed that wall thickness/pipe diameter equals. The dividing line is that thin-walled steel pipes are used when the wall thickness/pipe diameter is smaller than . Thick-walled straight-seam steel pipes are mostly used as blanks for hollow parts. Used on pressure-bearing and important pipelines.

Commonly used materials for thick-walled straight seam steel pipes are,,,,,,

Thick-walled straight seam steel pipes are mainly produced by double-sided submerged arc welding, and the products are bent. , jointing, internal welding, external welding, straightening, flat head and other multiple processes to meet relevant standard requirements.

Thick-walled straight-seam steel pipes are the best choice for large-scale pipeline projects, water and gas transmission projects, and urban pipeline network construction. The national west-to-east gas transmission uses this type of steel pipes to the tune of 10,000 tons, and the market prospects are broad.


Galvanized steel pipes are divided into cold-dip galvanized pipes and hot-dip galvanized pipes. The former has been banned, and the latter has been advocated by the country for temporary use. In the 1960s and 1970s, developed countries in the world began to develop new pipes and gradually banned galvanized pipes. China's Ministry of Construction and four other ministries and commissions have also issued documents clarifying that galvanized pipes will be banned from two years ago. Currently, galvanized pipes are rarely used in cold water pipes in newly built communities, and hot water pipes in some communities use galvanized pipes.
Hot-dip galvanized pipe reacts molten metal with an iron matrix to produce an alloy layer, thereby combining the matrix and the coating. Hot-dip galvanizing is to pickle the steel pipe first. In order to remove the iron oxide on the surface of the steel pipe, after pickling, it is cleaned in an aqueous solution of ammonium chloride or zinc chloride or a mixed aqueous solution of ammonium chloride and zinc chloride, and then sent to in a hot dip plating tank. Hot-dip galvanizing has the advantages of uniform coating, strong adhesion, and long service life. The hot-dip galvanized steel pipe matrix undergoes complex physical and chemical reactions with the molten plating bath to form a corrosion-resistant zinc-iron alloy layer with a tight structure. The alloy layer is integrated with the pure zinc layer and the steel pipe matrix. Therefore, it has strong corrosion resistance.
Cold-dip galvanized pipe is electro-galvanized. The amount of galvanizing is very small. Only its corrosion resistance is much different than that of hot-dip galvanized pipe. Regular galvanized pipe manufacturers, in order to ensure quality, most do not use electro-galvanizing (cold plating). Only small businesses with small scale and old equipment use electro-galvanizing, and of course their prices are relatively cheaper. At present, the Ministry of Construction has officially issued a notice to eliminate cold-galvanized pipes with backward technology. In the future, cold-galvanized pipes are not allowed to be used as water and gas pipes. The zinc layer of cold-dip galvanized steel pipe is an electroplated layer, and the zinc layer is layered independently from the steel pipe matrix. The zinc layer is thin, and the zinc layer simply adheres to the steel pipe matrix and falls off easily. Therefore, its corrosion resistance is poor. In new residential buildings, it is prohibited to use cold-dip galvanized steel pipes as water supply pipes.


Anti-corrosion straight seam steel pipe generally refers to the use of special processes to perform anti-corrosion treatment on ordinary steel pipes, so that the steel pipes have a certain anti-corrosion ability. They are generally used for waterproofing and rust prevention. , anti-acid and alkali, anti-oxidation and other properties. The base metal processes for anti-corrosion straight seam steel pipes include submerged arc welded straight seam steel pipes and high frequency straight seam steel pipes. The diameter of anti-corrosion submerged arc welded straight seam steel pipe is above, and the diameter of anti-corrosion high-frequency straight seam steel pipe is below. Corresponding anti-corrosion measures are taken for the inner and outer walls of steel pipes according to different needs and application environments. Commonly used ones include epoxy coal pitch anti-corrosion steel pipes, polyurethane anti-corrosion coatings, water diversion pipeline anti-corrosion non-toxic coatings, anti-corrosion polymer coatings, and anti-corrosion steel pipe inner walls. Cement mortar anti-corrosion, etc., anti-corrosion steel pipes are mainly used in engineering fields with special requirements or harsh environments. After the anti-corrosion straight seam steel pipe is treated with anti-corrosion, the steel pipe has the ability to resist corrosion and has the characteristics of waterproof, anti-rust, anti-acid and alkali, anti-oxidation and other properties.
Application fields of anti-corrosion straight seam steel pipes
, process pipelines for transporting corrosive media in petroleum and petroleum transportation pipelines, chemical pharmaceuticals, printing and dyeing and other industries
, fire protection and water supply pipelines for sprinkler and sprinkler systems It has excellent applicability
, highway power, communication, highway and other cable protection casing
, coal mine is suitable for underground coal mine water supply and drainage, underground grouting, positive and negative pressure ventilation, gas drainage, fire protection Sprinkler and other pipe networks
, sewage treatment, sewage treatment discharge pipes, sewage pipes and biological pool anti-corrosion projects
, power plant thermal power plant process water waste, return water transmission pipelines
, agricultural agricultural irrigation pipes, deep wells Pipes, drainage pipes and other networks, municipal projects are suitable for high-rise building water supply, heating network heating, tap water projects, gas transmission, underground water transmission and other pipelines.
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